>1)Linux Redhat AS 3.0 (Cpu,memory,disk,swap)
Sun has a linux agent. Check it out on sun.com.
>2)3com 3300 switch (Runs rmon probe)
You would need to build a proxy module. It's not as bad as it seems. There is a DE guide which explains how to build modules on docs.sun.com.
>3)3350 storage array
StorADE 2.4 will monitor a SE3350 and StorADE has an integration with SunMC.